Forward genetics and map-based cloning approaches.

Whereas reverse genetics strategies seek to identify and select mutations in a known sequence, forward genetics requires the cloning of sequences underlying a particular mutant phenotype. Map-based cloning is tedious, hampering the quick identification of candidate genes. With the unprecedented progress in the sequencing of whole genomes, and perhaps even more with the development of saturating marker technologies, map-based cloning can now be performed so efficiently that, at least for some plant model systems, it has become feasible to identify some candidate genes within a few months. This, in turn, will boost the use of forward genetics approaches, as applied (for example) to isolating genes involved in natural variation and genes causing phenotypic mutations as derived from (second-site) mutagenesis screens.